U.S. patent number 9,134,251 [Application Number 13/816,510] was granted by the patent office on 2015-09-15 for porous chemical indicator for gaseous media.
This patent grant is currently assigned to 3M Innovative Properties Company. The grantee listed for this patent is Duane D. Fansler, Neal A. Rakow, J. Christopher Thomas. Invention is credited to Duane D. Fansler, Neal A. Rakow, J. Christopher Thomas.
United States Patent |
9,134,251 |
Thomas , et al. |
September 15, 2015 |
**Please see images for:
( Certificate of Correction ) ** |
Porous chemical indicator for gaseous media
Abstract
Chemical indicators for acidic or basic gases include an inert,
porous substrate, an indicator dye or mixture of dyes contained
within at least some of the pores of the inert, porous substrate,
and an inert adhesive layer attached to the inert, porous
substrate. The porous substrate may be a microporous substrate.
Inventors: |
Thomas; J. Christopher (St.
Paul, MN), Rakow; Neal A. (Woodbury, MN), Fansler; Duane
D. (Dresser, WI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Thomas; J. Christopher
Rakow; Neal A.
Fansler; Duane D. |
St. Paul
Woodbury
Dresser |
MN
MN
WI |
US
US
US |
|
|
Assignee: |
3M Innovative Properties
Company (St. Paul, MN)
|
Family
ID: |
45874291 |
Appl.
No.: |
13/816,510 |
Filed: |
September 15, 2011 |
PCT
Filed: |
September 15, 2011 |
PCT No.: |
PCT/US2011/051767 |
371(c)(1),(2),(4) Date: |
April 10, 2013 |
PCT
Pub. No.: |
WO2012/040032 |
PCT
Pub. Date: |
March 29, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130189166 A1 |
Jul 25, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61385589 |
Sep 23, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N
31/221 (20130101); G01N 21/783 (20130101); G01N
31/22 (20130101); G01N 2021/7796 (20130101); B01L
2300/044 (20130101); A61B 17/083 (20130101); A61B
17/085 (20130101); G01N 21/78 (20130101); G01N
2035/00108 (20130101); B01L 2300/046 (20130101); A61B
10/0045 (20130101); G01N 2001/028 (20130101); B01L
2200/16 (20130101); G01N 2021/773 (20130101); Y10T
156/10 (20150115); G01N 2035/00148 (20130101) |
Current International
Class: |
G01N
21/75 (20060101); G01N 21/78 (20060101); G01N
31/22 (20060101); A61B 17/08 (20060101); A61B
10/00 (20060101); G01N 21/77 (20060101); G01N
1/02 (20060101); G01N 35/00 (20060101) |
Field of
Search: |
;422/83,84,85,86,87 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0263692 |
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Apr 1988 |
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EP |
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0901009 |
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Mar 1999 |
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EP |
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WO 2004/057314 |
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Jul 2004 |
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WO |
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WO 2004/059281 |
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Jul 2004 |
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WO |
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WO 2006/032719 |
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Mar 2006 |
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WO |
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Primary Examiner: White; Dennis M
Attorney, Agent or Firm: Olofson; Jeffrey M.
Claims
What is claimed is:
1. A chemical indicator comprising: an inert, porous substrate; an
indicator dye or mixture of dyes contained within at least some of
the pores of the inert, porous substrate, wherein the indicator dye
or mixture of dyes is coated on the inert, porous substrate
dissolved in a solvent and dried to remove the solvent, wherein the
solvent consists of methanol, ethanol, isopropanol, acetone, methyl
ethyl ketone, ethyl acetate, ethyl ether, tetrahydrofuran, or
dichloromethane; and an inert pressure sensitive adhesive layer
attached to the inert, porous substrate.
2. The chemical indicator of claim 1, wherein the inert, porous
substrate comprises a microporous substrate, wherein substantially
all of the pores are less than 1,000 micrometers in diameter.
3. The chemical indicator of claim 1, wherein the inert, porous
substrate comprises a polymeric porous substrate.
4. The chemical indicator of claim 3, wherein the polymeric porous
substrate comprises polyethylene, polypropylene or other
hydrocarbon polymer or mixture thereof.
5. The chemical indicator of claim 1, wherein the inert, porous
substrate comprises a membrane prepared by thermally induced phase
separation.
6. The chemical indicator of claim 1, wherein the indicator dye
comprises an acid indicator dye, or a base indicator dye.
7. The chemical indicator of claim 1, wherein the inert pressure
sensitive adhesive layer comprises an adhesive layer substantially
free of acid-containing and base-containing units.
8. The chemical indicator of claim 1, wherein the inert pressure
sensitive adhesive layer comprises a natural rubber adhesive, a
synthetic rubber adhesive, a poly-alpha-olefin adhesive, a styrene
block copolymer adhesive, a poly-(meth)acrylate adhesive, a
silicone adhesive or mixtures thereof.
9. The chemical indicator of claim 1, further comprising a
non-porous layer attached to the inert porous substrate by an
adhesive layer.
10. A device comprising: a case; and at least one chemical
indicator within the case, the chemical indicator comprising: an
inert, porous substrate; and an indicator dye or mixture of dyes
contained within at least some of the pores of the inert, porous
substrate, wherein the indicator dye or mixture of dyes is coated
on the inert, porous substrate dissolved in a solvent and dried to
remove the solvent, wherein the solvent consists of methanol,
ethanol, isopropanol, acetone, methyl ethyl ketone, ethyl acetate,
ethyl ether, tetrahydrofuran, or dichloromethane; and an inert
pressure sensitive adhesive layer attached to the inert, porous
substrate.
11. The device of claim 10, wherein the pressure sensitive adhesive
layer attaches the chemical indicator to the surface of the
case.
12. The device of claim 10, wherein the inert, porous substrate
comprises a microporous substrate, wherein substantially all of the
pores are less than 1,000 micrometers in diameter.
13. The device of claim 10, wherein the indicator dye comprises an
acid indicator dye or a base indicator dye.
14. The device of claim 10, further comprising additional chemical
indicators, wherein the additional chemical indicators may be the
same or different from the at least one chemical indicator.
15. The device of claim 10, wherein the case comprises a respirator
cartridge.
16. The device of claim 10, further comprising a non-porous layer
attached to the inert porous substrate by the inert pressure
sensitive adhesive layer.
17. The device of claim 16, further comprising a second adhesive
layer attached to the non-porous layer.
18. The device of claim 10, wherein the inert pressure sensitive
adhesive layer comprises a transparent pressure sensitive adhesive
layer.
19. A method of preparing a chemical indicator comprising:
providing an inert, porous substrate; providing an indicator dye
solution; applying the indicator dye solution to the inert, porous
substrate such that at least some of the indicator dye mixture
enters the pores of the inert, porous substrate; drying the inert,
porous substrate to remove the solvent, wherein the solvent
consists of methanol, ethanol, isopropanol, acetone, methyl ethyl
ketone, ethyl acetate, ethyl ether, tetrahydrofuran, or
dichloromethane; and applying a layer of inert pressure sensitive
adhesive to the porous substrate.
20. The method of claim 19, wherein applying a layer of inert
pressure sensitive adhesive to the porous substrate comprises
laminating an inert pressure sensitive adhesive layer to the porous
substrate.
Description
FIELD OF THE DISCLOSURE
The present disclosure pertains to chemical indicators for acidic
or basic gases, devices incorporating such indicators and methods
of preparing chemical indicators for acidic or basic gases.
BACKGROUND
A variety of techniques are used to detect the presence of acids,
acidic substances, bases and basic substances in liquids. For
example, electronic devices such as pH meters can be used or
chemical detection techniques such as Litmus paper can be used.
The detection of the presence of acids or bases in gases is more
difficult and is becoming increasingly important. In a variety of
work and other environments, acidic or basic gases may be present,
and their presence can provide a hazard to those exposed to these
gases. Techniques suitable for the detection of acids or bases in
liquids typically are not suitable for the detection of acids or
bases in gaseous media.
SUMMARY
The present disclosure comprises chemical indicators for acidic or
basic gases. The chemical indicators comprise an inert, porous
substrate, an indicator dye or mixture of dyes contained within at
least some of the pores of the inert, porous substrate, and an
inert adhesive layer attached to the inert, porous substrate. In
some embodiments, the porous substrate comprises a microporous
substrate.
Also disclosed are devices incorporating chemical indicators for
acidic or basic gases. The devices comprise a case, and at least
one chemical indicator within the case. The chemical indicator
comprises an inert, porous substrate, and an indicator dye or
mixture of dyes contained within at least some of the pores of the
inert, porous substrate, and an inert adhesive layer attached to
the inert, porous substrate. The porous substrate may comprise a
microporous substrate. In some embodiments, the case comprises a
respirator cartridge.
Further, methods of preparing chemical indicators for acidic or
basic gases are disclosed. The methods of preparing a chemical
indicator comprise providing an inert, porous substrate, providing
an indicator dye solution, and applying the indicator dye mixture
to the inert, porous substrate such that at least some of the
indicator dye mixture enters the pores of the inert, porous
substrate. A layer of inert adhesive is applied to the inert,
porous substrate. In some embodiments, the adhesive layer is
applied by laminating an inert adhesive layer to the porous
substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
The disclosure may be more completely understood in consideration
of the following detailed description of various embodiments of the
disclosure in connection with the accompanying drawings.
FIG. 1 shows a cross sectional view of a porous chemical indicator
of this disclosure.
FIG. 2 shows a cross sectional view of an alternative porous
chemical indicator of this disclosure.
In the following description of the illustrated embodiments,
reference is made to the accompanying drawings, in which is shown
by way of illustration, various embodiments in which the disclosure
may be practiced. It is to be understood that the embodiments may
be utilized and structural changes may be made without departing
from the scope of the present disclosure. The figures are not
necessarily to scale. Like numbers used in the figures refer to
like components. However, it will be understood that the use of a
number to refer to a component in a given figure is not intended to
limit the component in another figure labeled with the same
number.
DETAILED DESCRIPTION
A variety of environments, including work environments, may contain
acidic or basic gases that may be harmful to workers present. A
variety of protective clothing and devices have been developed to
protect against exposure to these acidic or basic gases. In
particular, respirators have been developed to protect the
respiratory system from damage by acidic or basic gases. Such
respirators often contain filter cartridges with materials to
absorb or otherwise neutralize the acidic or basic gases. When such
respirators are used, it is generally desirable to have a method to
determine an end of service life, i.e. the point at which the
respirator no longer provides protection from acidic or basic
gases. Frequently End of Service Life Indicators (ESLI) are used.
Such indicators provide a visual, electronic or other cue that the
respirator or filter cartridge within a respirator is approaching
the end of its useful life and should be replaced.
In this disclosure are presented porous chemical indicators that
can be used, among other uses, as ESLI for acidic or basic gas
respirator devices. The chemical indicators comprise an inert,
porous substrate, an indicator dye or mixture of dyes contained
within at least some of the pores of the inert, porous substrate,
and an inert adhesive layer attached to the porous substrate. In
some embodiments the porous substrate comprises a microporous
substrate. Examples of microporous substrates include films and
membranes. Microporous films and membranes have a structure that
enables fluids to flow through them. The effective pore size is at
least several times the mean free path of the flowing molecules,
namely from several micrometers down to about 100 Angstroms.
Typically a microporous substrate is one in which substantially all
of the pores have a diameter of less than 1,000 micrometers. More
typically microporous substrates have pore diameters of from 1 to
about 500 micrometers, or 1 to about 100 micrometers or even 1 to
about 10 micrometers.
As used herein, the term "indicator" refers to a device, layer or
series of layers that upon exposure to an analyte, such as an acid,
undergoes a detectable change. Typically the detectable change is a
visual change. When the visual change is a change in color, the
indicator is said to be "colorimetric".
As used herein, the term "acid gases or acidic gases" refers to
gases that contain some acidic component. The acidic component may
itself be a gas, such as, for example hydrogen chloride gas, but
the acidic component need not itself be a gas, but may merely be
present in the gas or gas mixture. Additionally, acidic gases may
not themselves be acids but acids may result from combination with
other materials present in the atmosphere.
As used herein, the term "base gases or basic gases" refers to
gases that contain some basic component. The basic component may
itself be a gas, such as, for example ammonia, but the basic
component need not itself be a gas, but may merely be present in
the gas or gas mixture. Additionally, basic gases may not
themselves be bases but bases may result from combination with
other materials present in the atmosphere.
As used herein, the term "inert" when used to describe porous
substrates or adhesive layers, means that the porous substrates or
adhesive layers are substantially unreactive with acidic or basic
gases and remain substantially physically and chemically unchanged
when exposed to acidic or basic gases. Typically, inert layers are
prepared from materials that are themselves substantially free of
acidic or basic components.
Disclosed herein are chemical indicators that comprise an inert,
porous substrate, an indicator dye or dye mixture contained within
at least some of the pores of the inert, porous substrate, and an
inert adhesive layer attached to the inert, porous substrate. The
chemical indicators of this disclosure are suitable for detecting
acidic or basic gases present within a gaseous media.
The chemical indicators of this disclosure comprise an inert,
porous substrate. The inert, porous substrate serves as a container
for the indicator dye or dye mixture. Additionally, the inert,
porous substrate acts as a diffusion layer, facilitating transport
of the acidic gas or basic gas to the indicator dye or dye mixture.
In some embodiments, the inert porous substrate may be opaque. Many
porous and microporous substrates are opaque, even if prepared from
optically transparent materials, because the surfaces and internal
structure of these substrates scatter visible light. In the present
disclosure, this opacity may be advantageous as it can provide a
background for monitoring changes in the indicator dye or dye
mixture, such as, for example, color changes.
A variety of materials can be used to prepare the inert, porous
substrate. Either inorganic or organic materials may be used. In
some embodiments, hydrocarbon-based polymeric materials are used.
Polyolefinic materials, such as, for example, polyethylene,
polypropylene, and the like and blends thereof are a particularly
useful class of materials for preparing the inert, porous
substrate.
In some embodiments, the inert, porous substrate comprises a
microporous membrane. Suitable microporous membranes for use as the
inert, porous substrate include those resulting from a phase
inversion method in which an initially homogeneous polymer solution
is cast and exposed to a cooler interface (e.g., a water bath or
chilled casting wheel), and phase separation is induced in the
solution film by lowering the temperature (thermally induced phase
separation or "TIPS"). Suitable TIPS films or membranes may possess
a broad range of physical film properties and microscopic pore
sizes. They may be relatively rigid or non-rigid substrates
prepared from any of a variety of polymers. TIPS membranes made
according to the teachings of U.S. Pat. Nos. 4,539,256 and
5,120,594 are suitable for use in this disclosure and may comprise
high density polyethylene (HDPE), polypropylene,
polyvinylidenefluoride (PVDF), polyethylene-vinyl alcohol copolymer
(e.g., available under the trade designation EVAL F101A from EVAL
Company of America (EVALCA), Houston, Tex.), for example. The
membrane may comprise a combination of materials such as a TIPS
HDPE or a polypropylene membrane coated with a hydrophilic polymer
(e.g., polyethylene-vinyl alcohol copolymer or EVAL).
Other useful materials suitable for use as the inert, porous
substrate include: non-rigid polymers and other materials including
nylon materials such as positively charged Nylon 6,6 materials
(e.g., those available under the trade designation Biodyne B from
Pall Corporation, Pensacola, Fla. and those available under the
trade designation Magnaprobe from GE Osmonics Labstore in
Minnetonka, Minn.); a hydrophilic treated polypropylene membrane
with 0.45 micrometer pore size, available under the trade
designation GHP-450 from Pall Corporation; polyolefins (with a
hydrophilic treatment); polyester; nitrocellulose; cellulose
acetate; hydrophilic polytetrafluoroethylene (PTFE); polycarbonate;
and the like. Additional useful materials include nonwoven, melt
blown, or spunbond webs made from, for example, polyolefins, nylon,
polyvinylidene fluoride (PVDF), and the like, prepared with small
effective fiber diameter. Also suitable are melt blown and spunbond
webs that are compressed with pressure to reduce substrate
thickness and pore size as described in U.S. Pat. No. 6,533,119.
Additional substrate materials include, particle-filled microporous
substrates are described in U.S. Pat. Nos. 6,264,864, 6,348,258,
4,777,073 and porous substrates prepared from nanosized electrospun
fibers as described in US Patent Publication 2006/094320.
Combinations of materials may be used in the inert, porous
substrate and the foregoing description is to be understood to
include the aforementioned materials alone and in combination with
other materials.
The chemical indicators of this disclosure also comprise an
indicator dye or dye mixture. The indicator dye or dye mixture
produces a detectable change, typically a color change, upon
exposure to a target analyte. In some embodiments the target
analyte is an acidic gas, in other embodiments the target analyte
is a basic gas.
A wide variety of materials may be used in the chemical indicators
of this disclosure as the indicator dye or dye mixture. Upon
exposure to an analyte, the indicator dye or dye mixture undergoes
a detectable change. Typically the detectable change is a
colorimetric change and is detectable with the naked eye. This
detectable change can take a variety of modes, such as, for
example, from a colored state to a colorless or less colored state,
from a colorless state to a colored state, or from one color to
different color.
Many indicator dyes can be used to detect either acidic or basic
gases. Generally, the indicator dye or dye mixture is in a form
such that a detectable change occurs upon exposure to the desired
analyte. For example, if it is desired that the indicator dye
detect the presence of an acidic gas, the indicator dye typically
is in a basic form. Similarly, if it is desired that the indicator
dye detect the presence of a basic gas, the indicator dye typically
is in an acidic form.
If the chemical indicator is designed to detect acidic gases, an
indicator dye or dye mixture is selected that upon exposure to
acidic species undergoes a detectable change, such as for example,
a color change. A wide range of such indicator dyes are available.
Various forms of indicator dyes or dye mixtures may be useful,
including, for example acidic or basic forms, and various salts
that provide for improved solubility or reactivity characteristics.
Suitable dyes may be located, for example, in "The Sigma-Aldrich
Handbook of Stains, Dyes, and Indicators", Floyd J. Green, 1990,
The Sigma-Aldrich Chemical Company, Inc. Examples of suitable dyes
for detecting acidic gases include, for example, Bromothymol Blue,
Methyl Red and Phenol Red, Bromocresol Purple, Bromocresol Green,
Phenophthalein, and Congo Red when used in their basic forms. Of
these, Bromothymol Blue, Methyl Red and Phenol Red, are
particularly suitable.
If the chemical indicator is designed to detect basic gases, an
indicator dye or dye mixture is selected that upon exposure to
basic species undergoes a detectable change, such as, for example,
a color change. A wide range of such indicator dyes are available.
Examples of suitable dyes for detecting basic gases include, for
example, the same indicators described above where the dyes are
present in their acidic forms.
The chemical indicators of this disclosure comprise an inert
adhesive layer attached to the inert, porous substrate. The inert
adhesive layer can serve to adhere a substrate or film to the
porous substrate or can serve as a mounting surface, permitting the
chemical indicator to be mounted directly to a variety of surfaces.
The inert adhesive layer is selected such that it does not interact
substantially with the indicator dye or mixture of indicator dyes.
Typically, the adhesive layer is substantially free of acidic or
basic moieties that can interact with or even react with the
indicator dye or dyes. Also, it is desirable that the adhesive
layer not solubilize the indicator dye or mixture of dyes.
A wide variety of adhesives are useful in the inert adhesive layer
of the chemical indicators of this disclosure. Typically the
adhesive is a pressure sensitive adhesive. Pressure sensitive
adhesive compositions are well known to those of ordinary skill in
the art to possess properties including the following: (1)
aggressive and permanent tack, (2) adherence with no more than
finger pressure, (3) sufficient ability to hold onto an adherend,
and (4) sufficient cohesive strength to be cleanly removable from
the adherend. Materials that have been found to function well as
pressure sensitive adhesives are polymers designed and formulated
to exhibit the requisite viscoelastic properties resulting in a
desired balance of tack, peel adhesion, and shear holding power.
Obtaining the proper balance of properties is not a simple
process.
Useful pressure sensitive adhesives include those based on natural
rubbers, synthetic rubbers, styrene block copolymers, acrylics,
poly-.alpha.-olefins, or silicones.
Useful natural rubber pressure sensitive adhesives generally
contain masticated natural rubber, from 25 parts to 300 parts of
one or more tackifying resins to 100 parts of natural rubber, and
typically from 0.5 to 2.0 parts of one or more antioxidants.
Natural rubber may range in grade from a light pale crepe grade to
a darker ribbed smoked sheet and includes such examples as CV-60, a
controlled viscosity rubber grade and SMR-5, a ribbed smoked sheet
rubber grade.
Another useful class of pressure sensitive adhesives are those
comprising synthetic rubber. Such adhesives are generally rubbery
elastomers, which are either self-tacky or non tacky and require
tackifiers. Self-tacky synthetic rubber pressure sensitive
adhesives include for example, butyl rubber, a copolymer of
isobutylene with less than 3 percent isoprene, polyisobutylene, a
homopolymer of isoprene, polybutadiene, such as "TAKTENE 220 BAYER"
or styrene/butadiene rubber. Butyl rubber pressure sensitive
adhesives often contain an antioxidant such as zinc dibutyl
dithiocarbamate. Polyisobutylene pressure sensitive adhesives do
not usually contain antioxidants. Synthetic rubber pressure
sensitive adhesives, which generally require tackifiers, are also
generally easier to melt process. They comprise polybutadiene or
styrene/butadiene rubber, from 10 parts to 200 parts of a
tackifier, and generally from 0.5 to 2.0 parts per 100 parts rubber
of an antioxidant. An example of a synthetic rubber is "AMERIPOL
1011A", a styrene/butadiene rubber available from BF Goodrich.
Styrene block copolymer pressure sensitive adhesives generally
comprise elastomers of the A-B or A-B-A type, where A represents a
thermoplastic polystyrene block and B represents a rubbery block of
polyisoprene, polybutadiene, or poly(ethylene/butylene), and
resins. Examples of the various block copolymers useful in block
copolymer pressure sensitive adhesives include linear, radial, star
and tapered styrene-isoprene block copolymers such as "KRATON
D1107P", available from Shell Chemical Co., and "EUROPRENE SOL TE
9110", available from EniChem Elastomers Americas, Inc.; linear
styrene-(ethylene-butylene) block copolymers such as "KRATON
G1657", available from Shell Chemical Co.; linear
styrene-(ethylene-propylene) block copolymers such as "KRATON
G1750X", available from Shell Chemical Co.; and linear, radial, and
star styrene-butadiene block copolymers such as "KRATON D1118X",
available from Shell Chemical Co., and "EUROPRENE SOL TE 6205",
available from EniChem Elastomers Americas, Inc. The polystyrene
blocks tend to form domains in the shape of spheroids, cylinders,
or plates that causes the block copolymer pressure sensitive
adhesives to have two phase structures. Resins that associate with
the rubber phase generally develop tack in the pressure sensitive
adhesive. Resins that associate with the thermoplastic phase tend
to stiffen the pressure sensitive adhesive.
Acrylic pressure sensitive adhesives generally have a glass
transition temperature of about -20.degree. C. or less and may
comprise from 100 to 80 weight percent of a C.sub.3-C.sub.12 alkyl
ester component such as, for example, isooctyl acrylate,
2-ethyl-hexyl acrylate, lauryl acrylate, and n-butyl acrylate and
from 0 to 20 weight percent of a reinforcing component such as, for
example, ethylene vinyl acetate, or styrene macromer. The acrylic
pressure sensitive adhesives may be self-tacky or tackified.
Poly-.alpha.-olefin pressure sensitive adhesives, also called
poly(1-alkene) pressure sensitive adhesives, generally comprise
either a substantially uncrosslinked polymer or a uncrosslinked
polymer that may have radiation activatable functional groups
grafted thereon as described, for example, in U.S. Pat. No.
5,209,971 (Babu, et al). The poly-.alpha.-olefin polymer may be
self tacky and/or include one or more tackifying materials. Useful
poly-.alpha.-olefin polymers include, for example, C.sub.3-C.sub.18
poly(1-alkene) polymers, preferably C.sub.5-C.sub.12
.alpha.-olefins and copolymers of those with C.sub.3 and more
preferably C.sub.6-C.sub.8 and copolymers of those with
C.sub.3.
Suitable silicone pressure sensitive adhesives are formed from
mixtures of compounds in which are present vinylic groups and
hydrosilane groups. Vinylic groups comprise terminal carbon-carbon
double bonds and hydrosilane groups comprise at least one terminal
Si--H bond. Typically, elastomeric polymers are formed through the
hydrosilylation reaction shown below:
A-CH.dbd.CH.sub.2+B--Si--H.fwdarw.A-CH.sub.2--CH.sub.2--Si--B
Hydrosilylation reaction
Typically, a catalyst, such as a noble metal catalyst such as a
platinum, palladium, rhodium or iridium catalyst, is used to
catalyze the hydrosilylation reaction. The compound containing the
vinylic group may be a silicone, the compound containing the
hydrosilane may be a silicone or both may be silicones. As used
herein, the terms "silicone" and "siloxane" are used
interchangeably and refer to units with dialkyl or diaryl siloxane
(--SiR.sub.2O--) repeat units. Examples of silicone pressure
sensitive adhesives prepared by hydrosilylation are described, for
example, in U.S. Pat. No. 5,169,727 (Boardman).
In some embodiments, it may be desirable that the adhesive layer be
optically transparent or optically clear. Unless otherwise
indicated, "optically transparent" refers to an article, film or
adhesive that has a high light transmittance over at least a
portion of the visible light spectrum (about 400 to about 700 nm).
Unless otherwise indicated, "optically clear" refers to an article,
film or adhesive that has a high light transmittance over at least
a portion of the visible light spectrum (about 400 to about 700
nm), and that exhibits low haze. Optical transparency can permit
the chemical indicator to be monitored from the adhesive side as
well as from the inert, porous substrate side.
In some embodiments, the adhesive layer may be a transfer tape. The
term "transfer tape" as used herein refers to a double sided
adhesive tape that has adhesive on both exposed surfaces. In some
transfer tapes, the exposed surfaces are simply the two surfaces of
a single adhesive layer. Other transfer tapes are multilayer
transfer tapes with at least two adhesive layers that may be the
same or different, and in some instances intervening layers that
mayor may not be adhesive layers. For example, a multi-layer
transfer tape may be a 3 layer construction with an adhesive layer,
a film layer and another adhesive layer. The film layer can provide
handling and/or tear strength or other desirable properties.
Typically, transfer tapes are provided on a release substrate, such
as a release liner, to aid handling and delivery of the transfer
tape.
A variety of optional additional layers may be present in the
chemical indicators of this disclosure. In some embodiments, for
example, it may be desirable to include a non-porous substrate
layer to the adhesive layer of the chemical indicator. This
non-porous substrate layer may be a film or sheet or it may be a
more rigid substrate such as glass or ceramic. In some embodiments,
the non-porous substrate may be removable, such as a release liner.
In other embodiments, the film or sheet may be tinted or colored in
order to help provide a color contrast for the indicator dye. For
example, it may be desirable, in some embodiments, to have a white
film attached to the adhesive layer so that a color change in the
indicator dye, such as from white to red or pink, is more
noticeable. In this way an observer, when monitoring the chemical
indicator, could look through the inert, porous substrate to the
adhesive layer covered with a film layer and better see the
colorimetric change of the indicator dye. Additionally, the film or
sheet may be transparent to allow an observed to monitor the
chemical indicator by looking through the film and adhesive layers.
The film or sheet may be prepared from any suitable material, for
example metal foils or polymeric materials such as polyethylene,
polypropylene, other polyolefinic polymers, polyesters and the
like. In some embodiments, the film or sheet is a tape backing, and
the adhesive layer and the film together form a tape that can be
laminated to the inert, porous substrate to form the chemical
indicator.
In some embodiments in which a film is included in the chemical
indicator construction, it may be desirable to have indicia printed
on the film, either before or after the film is incorporated into
the chemical indicator. For example, square, rectangular or other
shaped figures may be printed on the film to indicate an area for
the observer to look to observe the color change of the indicator.
In other embodiments, a reference color strip or layer may be
printed on the film to mimic either the initial or activated state
of the indicator. For example, if the indicator changes to a red
color upon activation, a red strip may be printed on the film layer
with accompanying text stating for example, "When the indicator is
this color, acid gases are present". The indicia may also be a text
message with information or instructions for the observer, such as,
for example, "Check this indicator strip before opening door to
storage room".
In some embodiments, it may be desirable to have a second adhesive
layer. This second adhesive layer is present on at least a portion
of the exterior surface of the non-porous substrate. The exterior
surface is the one opposite to the surface that is attached to the
inert adhesive layer of the chemical indicator. This adhesive layer
can be used, for example, to attach the chemical indicator to a
surface. This second adhesive layer can comprise the same adhesive
material as the inert adhesive layer, or it may comprise a
different adhesive material. This adhesive layer may be continuous
or discontinuous and may contain a microstructured surface. The
second adhesive layer can be covered with a release liner to
protect the adhesive surface prior to attachment to a surface. This
release liner can contain a microstructured surface which can
generate a microstructured topography onto the surface of the
second adhesive layer when the release liner is removed. Such
surface structuring of adhesives can be beneficial to aid air
egress when the adhesive layer is applied to a surface to form an
adhesive bond.
Referring to the figures, FIG. 1 shows a cross sectional view of a
porous chemical indicator of this disclosure. Porous chemical
indicator 100 comprises inert porous substrate 110 which contains
indicator dye or dyes (not shown) and inert adhesive layer 120.
FIG. 2 shows a cross sectional view of an alternative embodiment of
a porous chemical indicator of this disclosure. Porous chemical
indicator 200 comprises inert porous substrate 210 which contains
indicator dye or dyes (not shown) inert adhesive layer 220, film
layer 230, and optional adhesive layer 240 and optional release
liner 250. As described above, adhesive layers 220 and 240 may be
the same or different. In some embodiments, adhesive layers 220 and
240 are both optically clear adhesive layers. Film layer 230 may be
optically transparent. Adhesive layer 220 and film layer 230
together may comprise a tape article that has been laminated to
porous substrate 210.
The chemical indicators of this disclosure can be used to form a
variety of different devices and articles. Additionally, the
indicators can be incorporated into existing devices and articles
to provide an indicating function to those devices and
articles.
Among the useful devices which can be prepared using the indicators
of this disclosure are ESLI, or End of Service Life Indicators. As
mentioned above, ESLI are useful with devices such as air purifying
respirators, to provide an indication of end of the useful service
life of the respirator. In some cases, regulations, such as
government regulations, require that an ESLI device be employed
where respirators are used unless a change out schedule is used.
Patent references that refer to ESLIs in particular include U.S.
Pat. No. 1,537,519 (Yablick), U.S. Pat. No. 3,966,440 (Roberts),
U.S. Pat. No. 4,146,887 (Magnante), U.S. Pat. No. 4,154,586 (Jones
et al), U.S. Pat. No. 4,155,358 (McAllister et al.), U.S. Pat. No.
4,326,514 (Eian), U.S. Pat. No. 4,421,719 (Burleigh), U.S. Pat. No.
4,530,706 (Jones), U.S. Pat. No. 4,597,942 (Meathrel), U.S. Pat.
No. 4,684,380 (Leichnitz), U.S. Pat. No. 4,847,594 (Stetter), U.S.
Pat. No. 5,297,544 (May et al.), U.S. Pat. No. 5,323,774
(Fehlauer), U.S. Pat. No. 5,376,554 (Vo-Dinh), U.S. Pat. No.
5,512,882 (Stetter et al.), U.S. Pat. No. 5,666,949 (Debe et al.
'949), U.S. Pat. No. 5,659,296 (Debe et al. '296), U.S. Pat. No.
6,375,725 B1 (Bernard et al.), U.S. Pat. No. 6,497,756 B1 (Curado
et al.) and U.S. Pat. No. 6,701,864 B2 (Watson, Jr. et al.); US.
Patent Application Publication Nos. US 2004/0135684 A1 (Steinthal
et al.), US 2004/0189982 A1 (Galarneau et al.), US 2004/0223876 A1
(Kirollos et al.) and US 2005/0188749 A1 (Custer et al.); and PCT
Published Patent Application No. WO 2004/057314 A2.
Additionally, the chemical indicators of this disclosure can be
used as passive monitors to provide a warning of acidic gas or
basic gas release. For example, the chemical indicators can be
mounted on a wall outside of a storage facility, processing
facility and the like to provide a warning by a detectable change
upon exposure to acidic or basic gases. For example, the chemical
indicator could be adhered to the window of a door at the entrance
to a storage facility where acidic or basic gases are stored. A
worker could check the chemical indicator before opening the door
to determine if there has been an accidental release of acidic or
basic gases.
A variety of methods can be used to prepare the chemical indicators
of this disclosure. For example, an inert, porous substrate can be
provided. This inert, porous substrate can be purchased or prepared
by the methods described above. In some embodiments the inert,
porous substrate is a polypropylene TIPS membrane as described
above. This inert, porous substrate can be coated with a solution
of an indicator dye, or mixture of dyes, dissolved in a solvent.
Any suitable solvent can be used, particularly suitable ones
include: alcohols such as methanol, ethanol, isopropanol and the
like; ketones such as acetone and methyl ethyl ketone; esters such
as ethyl acetate; ethers such as ethyl ether and tetrahydrofuran;
and halocarbons such as dichloromethane. Suitable dyes to prepare
acid gas indicators include, for example, Bromothymol Blue, Methyl
Red, and Phenol Red. In some embodiments, the indicator dye is
dissolved in ethanol. An aqueous base, such as sodium hydroxide or
potassium hydroxide, can be added to make the formed indicator
solution basic.
The dye solution may include a variety of additional property
modifiers, as long as these property modifiers do not interfere
with the function of the indicator dye or dye mixture. Examples of
property modifiers that can be used include, for example, wetting
agents, UV stabilizers, antistatic agents, gel-forming agents,
colorants, slip modifiers, thixotropic agents, tack promoting
agents, tack reducing agents, foaming agents, antifoaming agents,
flow or other rheology control agents, waxes, oils, plasticizers,
binders, antioxidants, fungicides, bactericides, organic and/or
inorganic filler particles, leveling agents, opacifiers,
dispersants, and the like.
The dye solution can be coated in a variety of ways using a variety
of different types of equipment. For example, when carried out on a
small scale, such as in a laboratory, the coating may be carried
out using a micropipette. For larger scale coating, coaters such as
spray coaters, gravure coaters, curtain coaters, fluid bearing die
coaters or printers such as, for example, inkjet printers can be
used. After coating, the coated inert, porous substrate may be
dried to remove the solvent. This drying can be done at room
temperature or at elevated temperature by using, for example, an
oven, such as a forced air oven.
To the inert, porous substrate with the indicator dye coated on it,
is laminated a layer of inert adhesive. As described above, this
adhesive layer may be in the form of a transfer tape or a tape with
a backing. If a transfer tape is used, additional layers may be
laminated to the exposed adhesive surface, or the exposed adhesive
surface may be covered with a release liner which can be removed to
attach the chemical indicator to a surface. It may be desirable to
laminate these additional layers one layer at a time or it may be
desirable to prepare a multilayer adhesive construction and
laminate this construction to the inert, porous substrate with the
indicator dye coated on it. This multilayer adhesive construction
can include multiple adhesive layers, and/or film layers as long as
there is an inert adhesive layer capable of being laminated to the
inert, porous substrate.
The present disclosure includes the following embodiments.
Among the embodiments are chemical indicators. A first embodiment
includes a chemical indicator comprising: an inert, porous
substrate; an indicator dye or mixture of dyes contained within at
least some of the pores of the inert, porous substrate; and an
inert adhesive layer attached to the inert, porous substrate.
Embodiment 2 is the chemical indicator of embodiment 1, wherein the
inert, porous substrate comprises a microporous substrate, wherein
substantially all of the pores are less than 1,000 micrometers in
diameter.
Embodiment 3 is the chemical indicator of embodiment 2, wherein
substantially all of the pores are from 1-500 micrometers in
diameter.
Embodiment 4 is the chemical indicator of embodiment 2, wherein
substantially all of the pores are from 1-100 micrometers in
diameter.
Embodiment 5 is the chemical indicator of embodiment 2, wherein
substantially all of the pores are from 1-10 micrometers in
diameter.
Embodiment 6 is the chemical indicator of any of embodiments 1-5,
wherein the porous substrate comprises a polymeric porous
substrate.
Embodiment 7 is the chemical indicator of embodiment 6, wherein the
polymeric porous substrate comprises polyethylene, polypropylene or
other hydrocarbon polymer or mixture thereof.
Embodiment 8 is the chemical indicator of any of embodiments 1-7,
wherein the inert, porous substrate comprises a membrane prepared
by thermally induced phase separation.
Embodiment 9 is the chemical indicator of embodiment 8, wherein the
membrane comprises polypropylene.
Embodiment 10 is the chemical indicator of any of embodiments 1-9,
wherein the indicator dye comprises an acid indicator dye, or a
base indicator dye.
Embodiment 11 is the chemical indicator of any of embodiments 1-10,
wherein the inert adhesive layer comprises an adhesive layer
substantially free of acid-containing and base-containing
units.
Embodiment 12 is the chemical indicator of any of embodiments 1-11,
wherein the inert adhesive layer comprises a natural rubber
adhesive, a synthetic rubber adhesive, a poly-alpha-olefin
adhesive, a styrene block copolymer adhesive, a poly-(meth)acrylate
adhesive, a silicone adhesive or mixtures thereof.
Embodiment 13 is the chemical indicator of any of embodiments 1-12,
further comprising a non-porous layer attached to the inert porous
substrate by an adhesive layer.
Embodiment 14 is the chemical indicator of embodiment 13, wherein
the non-porous layer comprises a film or tape backing.
Embodiment 15 is the chemical indicator of any of embodiments
13-14, further comprising a second adhesive layer adjacent to the
non-porous layer.
Embodiment 16 is the chemical indicator of embodiment 15, wherein
the second adhesive layer comprises the same adhesive as the inert
adhesive layer.
Embodiment 17 is the chemical indicator of embodiments 15, wherein
the second adhesive layer comprises an adhesive different from the
inert adhesive layer.
Embodiment 18 is the chemical indicator of any of embodiments
15-17, wherein the second adhesive layer comprises and optically
clear adhesive layer.
Embodiment 19 is the chemical indicator of any of embodiments
15-18, further comprising a release liner attached to the second
adhesive layer.
Among the embodiments of this disclosure are devices. Embodiment 20
comprises a device comprising: a case; and at least one chemical
indicator within the case, the chemical indicator comprising: an
inert, porous substrate; and an indicator dye or mixture of dyes
contained within at least some of the pores of the inert, porous
substrate; and an inert adhesive layer attached to the inert,
porous substrate.
Embodiment 21 is the device of embodiment 20, wherein the adhesive
layer attaches the chemical indicator to the surface of the
case.
Embodiment 22 is the device of any of embodiments 20-21, wherein
the inert, porous substrate comprises a microporous substrate,
wherein substantially all of the pores are less than 1,000
micrometers in diameter.
Embodiment 23 is the device of embodiment 22, wherein substantially
all of the pores are from 1-500 micrometers in diameter.
Embodiment 24 is the device of embodiment 22, wherein substantially
all of the pores are from 1-100 micrometers in diameter.
Embodiment 25 is the device of embodiment 22, wherein substantially
all of the pores are from 1-10 micrometers in diameter.
Embodiment 26 is the device of any of embodiments 20-25, wherein
the indicator dye comprises an acid indicator dye or a base
indicator dye.
Embodiment 27 is the device of any of embodiments 20-26, further
comprising additional chemical indicators, wherein the additional
chemical indicators may be the same or different from the at least
one chemical indicator.
Embodiment 28 is the device of any of embodiments 20-27, wherein
the case comprises a respirator cartridge.
Embodiment 29 is the device of any of embodiments 20-28, wherein
the inert adhesive layer comprises a transparent adhesive
layer.
Embodiment 30 is the device of any of embodiments 20-29, further
comprising a non-porous layer attached to the inert porous
substrate by the inert adhesive layer.
Embodiment 31 is the device of embodiment 30, further comprising a
second adhesive layer attached to the non-porous layer.
Embodiment 32 is the device of any of embodiments 30-31, wherein
the non-porous layer comprises a film or tape backing.
Embodiment 33 is the device of any of embodiments 30-32, wherein
the non-porous layer comprises a transparent layer.
Embodiment 34 is the device of embodiment 31, wherein the second
adhesive layer comprises the same adhesive as the inert adhesive
layer.
Embodiment 35 is the device of embodiment 31, wherein the second
adhesive layer comprises an adhesive different from the inert
adhesive layer.
Embodiment 36 is the device of any of embodiments 31 or 34-35,
wherein the second adhesive layer comprises and optically clear
adhesive layer.
Embodiment 37 is the device of any of embodiments 31 or 34-36,
further comprising a release liner attached to the second adhesive
layer.
Among the embodiments of this disclosure are methods of preparing
chemical indicators. Embodiment 38 includes the method of preparing
a chemical indicator comprising: providing an inert, porous
substrate; providing an indicator dye solution; applying the
indicator dye solution to the inert, porous substrate such that at
least some of the indicator dye mixture enters the pores of the
inert, porous substrate; and applying a layer of inert adhesive to
the porous substrate.
Embodiment 39 is the method of embodiment 38, wherein applying a
layer of inert adhesive to the porous substrate comprises
laminating an inert adhesive layer to the porous substrate.
Embodiment 40 is the method of any of embodiments 38-39, further
comprising drying the inert, porous substrate after applying the
indicator dye solution.
EXAMPLES
These examples are merely for illustrative purposes only and are
not meant to be limiting on the scope of the appended claims. All
parts, percentages, ratios, etc. in the examples and the rest of
the specification are by weight, unless noted otherwise. Solvents
and other reagents used were obtained from Sigma-Aldrich Chemical
Company; Milwaukee, Wis. unless otherwise noted.
TABLE-US-00001 Table of Abbreviations Abbreviation or Trade
Designation Description TIPS Porous polypropylene membrane made
according to the teachings of U.S. Pat. Nos. 5,120,594 and
5,238,623. Dye-1 Methyl Red, (CAS# 76-59-5). Adhesive-1 Transfer
tape prepared as described in U.S. Pat. No. 5,859,088, Example 1.
Adhesive-2 Transfer Tape of 3M OPTICALLY CLEAR ADHESIVE 8172,
commercially available form 3M Company, St. Paul, MN. Tape-1 Tape
of 3M SCOTCH MAGIC TAPE 810, commercially available from 3M
Company, St. Paul, MN. Respirator A 3M Organic Vapor Cartridge 6001
from 3M Company, Cartridge St. Paul, MN, filled with of 46.0 g of
GG carbon. GG carbon Commercially available from Kuraray Chemical
Company, Osaka, Japan.
Synthesis Examples
Synthesis Example S1
Preparation of Dye Solution
A solution of Dye-1 was prepared in ethanol solution using the
reagents listed in Table S1. The solid dye was placed in a glass
vial, ethanol was added to dissolve the dye, and 1.0 N NaOH (aq)
was added to basify the solution.
TABLE-US-00002 TABLE S1 1.0N NaOH Dye amount EtOH amount (aq)
amount Dye (mg) (.mu.L) (.mu.L) Dye-1 3.4 945 57
Example 1
A sample of TIPS membrane was coated with the Dye-1 solution
prepared in the Synthesis Example S1. The dye solution was
deposited onto the membrane using a micropipet to place 2.0
microliters of dye solution on the membrane. The sample was then
dried in air in the dark for several hours. sensor devices were
prepared by laminating the coated TIPS membrane to an adhesive or a
tape as described in Table 1 below. The adhesive laminated sensor
device was attached to a sample Respirator Cartridge. The
Respirator Cartridge with sensor device attached was exposed to an
SO.sub.2 flow of 32 liters per minute (Lpm) at 43% relative
humidity (RH) and 9.2 ppm of SO.sub.2 gas with the concentration of
SO.sub.2 at the outlet side monitored for breakthrough. The sensor
devices were monitored using an Olympus C-5060 CAMEDIA camera with
aperture 3.2, shutter speed 1/8, close focus, and delayed flash.
The results of the camera and outlet monitor are summarized in
Table 2 below.
TABLE-US-00003 TABLE 1 Example Adhesive Layer 1A Adhesive-1 1B
Adhesive-2 1C Tape-1
TABLE-US-00004 TABLE 2 Elapsed Outlet Time Monitor (Hr:Min) Example
1A Example 1B Example 1C (ppm SO.sub.2) 0:00 Yellow Yellow Yellow
0.0 2:15 Yellow Yellow Yellow 0.0 4:00 Yellow Yellow Yellow 0.0
6:20 Yellow Yellow Yellow 0.0 21:45 Red Red Red 0.1
Example 2
A sample of TIPS membrane was coated with the Dye-1 solution
prepared in the Synthesis Example S1. The dye solution was
deposited onto the membrane using a micropipet to place 2.0
microliters of dye solution on the membrane. The sample was then
dried in air in the dark for several hours. Sensor devices were
prepared by laminating the coated TIPS membrane to an adhesive or a
tape as described in Table 3 below. The adhesive laminated sensor
device was attached to a sample Respirator Cartridge. The
Respirator Cartridge with sensor device attached was exposed to an
SO.sub.2 flow of 32 liters per minute (Lpm) at 43% relative
humidity (RH) and 8.3 ppm of SO.sub.2 gas with the concentration of
SO.sub.2 at the outlet side of the Respirator Cartridge monitored
for breakthrough. The sensor devices were monitored using an
Olympus C-5060 CAMEDIA camera with aperture 3.2, shutter speed 1/8,
close focus, and delayed flash. The results of the camera and
outlet monitor are summarized in Table 4 below.
TABLE-US-00005 TABLE 3 Example Adhesive Layer 2A Adhesive-1 2B
Adhesive-2 2C Tape-1
TABLE-US-00006 TABLE 4 Elapsed Outlet Time Monitor (Hr:Min) Example
2A Example 2B Example 2C (ppm SO.sub.2) 0:00 Yellow Yellow Yellow
0.0 4:05 Yellow Yellow Yellow 0.0 6:00 Yellow Yellow Yellow 0.0
8:00 Yellow Yellow Yellow 0.0 23:45 Red Red Red 0.0 25:40 Red Red
Red 0.1
* * * * *